I have a CEL PO420 that keeps coming up for the past 5 months... it would bother me for the first two months, then i found out what it was - it had something to do with my car's CAT system (
well, the light usta come on just about every time i hit half tank of gas - then I'd reset it again ands the light wouldn't come back on again until i hit half tank again.
for the last two months, i just ignored the light and it stayed on for those several weeks. I've grown to just pretend that it wasn't there.
now for the past 2 weeks, i keep forgetting about it being on. but during my drive, it seems to magically attract my attention... hmmmmmmmm
I decided to reset it again for the first time in 2 months. This time i reset it right before making the 300 mile trek out to Las Vegas last weekend - and sure enough, the light came on again within the first 150 miles (about 1/2 tank)
i ignored it... but when coming back from Vegas, i noticed that the light was not ON all the time... it only turned on at half tank, but was off all before that point (i wasn't really paying attention to it, up until the point when it turned ON again)
Now tonight, I actually witnessed the light turn ON again... then drove 10 miles to my parents with the light ON and during that time, i watched the light turn OFF... its been OFF ever since - but i assume it will be back again.
how weird is it that a CEL will just "fix it-self"?
...is this totally unheard-of